In a modern cellular radio communication system, a base station or another element of a network infrastructure schedules uplink and downlink transmission opportunities to terminal devices. With respect to uplink scheduling, typically separate communication resources are scheduled to the terminal devices so as to avoid collisions. Some cellular communication systems employ spatial multiplexing, e.g. multi-user multiple-input-multiple-output (MU-MIMO), to schedule at least two terminal devices to transmit in the same time-frequency resources. The at least two terminal devices may be separated in the space domain by using multiple reception antennas and appropriate signal processing in the base station.